1. Field of the Invention
The present invention relates generally to cathode ray tube displays, and more specifically to designs for a cathode ray tube having multiple electron beam guns.
2. Description of the Prior Art
The cathode ray tube, in general, has a long history as a display device. Initially available as a monochrome display, and later available to display colors using separate controls for red, green and blue, the CRT has been the display device of choice for televisions and similar products such as computer monitors. Although alternative display technologies are now being utilized for television and computer displays, primarily in the area of very small devices, the CRT remains the display technology of choice for many applications.
This is due primarily to the many advantages of available CRT devices. These advantages include screen brightness and resolution. Color reproduction of CRTs is very good, and the drive circuitry required to control them is relatively simple and well understood. CRTs can be manufactured easily, and relatively inexpensively, and have a fairly long product life.
Other technologies are replacing CRTs in some areas, primarily due to limitations of the CRT technology. These limitations include the relatively large front to back dimension, or depth, of a CRT of a given size. Additionally, especially in the larger size devices, the weight of the tube becomes significant. These considerations tend to limit the maximum size of a CRT; an upper limit of approximately 30 to 40 inches, measured diagonally, is about the best that can be achieved using current technology. Current CRT technology also usually requires a curved face plate to withstand atmospheric pressure, especially in the larger sizes.
These limitations have generated significant research into alternative display technologies. Examples of such technology include liquid crystal displays (LCD) and field emission displays (FED). These displays overcome the size and weight limitations of traditional CRT technology, but have limitations of their own. Typically, these limitations are found in those areas which are the strengths of CRT displays. Limitations in alternate technologies typically include brightness and color problems, and manufacturing rejects, particularly with larger size displays.
Numerous attempts have been made to improve CRT technologies to retain its advantages, but to overcome some of its drawbacks. In order to enable larger displays to be built, for example, one approach has been to include multiple electron guns in a single picture tube. These electron guns each sweep a portion of the face of the display, theoretically allowing very large displays to be made.
However, designs along these lines which have been proposed in the past have not been easily manufacturable. Although the theories behind this design approach seem somewhat promising, the practicality of the various designs which have been proposed are too low to make them production-worthy. Therefore, the use of multiple electron gun devices has met with very limited success in the marketplace.
It would be desirable to provide a cathode ray tube device which is inexpensive and easy to manufacture, and which overcomes some the drawbacks of traditional CRT technology. Such a device can preferably be made very large compared to traditional CRT devices, and be provided with a high resolution, flat display. Such an improved device will also preferably have a relatively small depth, allowing fairly thin and light weight devices to be produced.